Electrical insulation.



W. A. ISHLER.

ELECTRICAL INSULATION.

APPLICATION FILED SEPT. 11. 1916.

Patented Apr. 24, 1917.

lnverwtorz Willisfllshler;

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EIQEGTRTG GtlMPANY, [a

l. 23,$8ll. Specification o Application filed September ing eflects ofhigh frequency and which are of general application to various types ofapparatus.

It has been discovered that films or layers of insulating oils, at leastof such oils as are now commonly used for submerging electricalapparatus, are particularly capable of maintaining high insulatingcharacteristics under the high frequencies to which some electricalapparatus, particularly transformers, are occasionally subjected. Othercommon insulating materials and structures .are liable to unexpectedfailures under the application of high frequencies. By my invention Tsecure in insulating barriers or pads the advantages of this property ofoil, as well as its better known insulating properties, by employingtotally inclosed impervious casings containing oil as in the form offilms or layers, preferably in the form of sheets of oil soaked fibrousmaterial. At one or both sides of the oil layer may be applied one ormore thicknesses of other insulating materials as conditions maydictate, for example to render the whole barrier more or less fireproof-A structure of this kind may be made in; the form of a fairly flexiblepad which may be wrapped around the part to be insulated-thereby. Such astructure is self contained and is protected against modification byoutside influences. The oil thereof cannot be displaced .norabsorbmoisture or other foreign fluids and thereby the pad lose itsexpected strength. The pad may therefore be ap- Better: Pate PatentedApr. 2 ft, third.

eral application, that is, is applicable both to devices submerged inoil and to those not submerged in oil, such as, for example, air blasttransformers; in both cases the enveloping casing retains the oil of theinsulating structure in its original quantity and purity. It. is evenpossible therefore by employing my invention to obtain some of theadvantages of oil insulation in apparatus not submerged in oil.

in the accompanying drawing and the following detailed description Ihave illustrated and described the best embodiment of my invention thatT am nowaware of, and such as T have found after a long course of tests,to possess very desirable characteristics. Figure l is an elevation ofan insulating barrier or pad embodying my invention such as is suitablefor use between the primary and secondary windings of smalltransformers. Figs. 2 and 3 are sections thereof respectively "on thelines 2-2 and 33 of Fig. 1. Fig. 4 is a perspective of the pad of Fig. lin substantially the form it assumes in the transformer of Fig. 5. Fig.5 is a plan view of a transformer provided with pads such as areillustrated in the preceding figures.

The pad of the drawing is made up of a number of layers of differentinsulating materials. The center layer 10 comprises a sheet of blottingpaper thoroughly soaked or saturated with insulating oil, for examplesuch oil as is now used for submerging transformers. At each side ofthis sheet of oil soaked blotting paper is a sheet ll of pastedrnica(that is, scraps of mica film pasted together into the form of a sheetand thoroughly compressed) between thicknesses of paper. Totallyinclosingthese sheets of insulating materials is a wrapping 12 ofvarnished cambric which is impervious to most fluids.

In applying the impervious wrapping of varnished cambric to produce thepad illustrated in the drawing, the oil soaked blotting paper and themica and paper sheets are assembled upon substantially the center of asheet of varnished cambric cut to the, requisite size. ()ne edge, forexample the near edge of the varnished cambric, is then folded over thetop mica sheet to the position indicated by the dotted line 15 ofFig; 1. The opposite or far edge of the cambric is likewise folded, butin the opposite direcarethen folded over and thoroughly stuck together,for example in the manner illustrated in Fig. 2. The overlapping edgesmay be shellacked to form tight joints. This manner of folding thevarnished cambric produces a totally inclosed impervious caseor'wrapping.

As this pad is applied to the transformer of Fig. 5, it assumes a shapesomething like that illustrated in perspective Fig. 4." In Fig. 5 twosuch pads are shown in position in a transformer. The windings of thistransformer surround the middle leg of the core 20. The windingscomprise two low potential windings 21 and 22 and a hugh potentialwinding of two coils 23 and 24 between the two low potential windings.Ventilating spaces 25 are left between the low potential winding 21 andthe high potential winding, and likewise an annular ventilating space 26is leftbetween the two coils 23 and 24: of the high potential winding.After'the low potential winding 22 is applied to the core. a barrier orpad 30, such as has .been described hereinbefore, is wrapped around thesame and over this is placed the high potential winding. On the outsideof the high potential winding is likewise placed a similar barrier orpad 31.

and the low potential winding 21 is placed outside this barrier. Such atransformer may safely be impregnated with insulating materials afterassembly as is\now a common practice, for the totally inclosingimpervious wrapping thoroughly excludes the impregnating material fromthe'absorbent sheet of the pad and retains the oil thereof. Shortcircuits even 010% to the pad, cannot entirely destroy the insulatingproperties of the pad due to the fire resisting qualities of the micasheets. As will be apwhether the transformer of Fig. 5 is submerged inoil or not during operation, some of the advantages of oil insulationare secured between the primary and secondary windings. 1

While I have described the principleof my invention and the 'best mode Ihave contemplated for applying this principle, other modifications willoccur to those skilled in this art and I aim in the appended claims tocover all modifications which do not involve a departure from the spiritand scope of my invention.

a What I claim as new and desire to secure by Letters Patent of theUnited States, is,

1- An insulation barrier comprising a relaatively thin totally inclosedcasing of an insulating material impervious to oil and a film of oilcontained therein.

2. An insulating barrier comprising a relatively thin impervious totallyinclosed casing and oil therein.

3. An' insulating barrier comprising an oil soaked absorbent sheet andan impervious wrapping totally inclosing the same.

4. An insulating 'barriercomprising an oil soaked absorbent sheet, asheet of fire resistant material at each side thereof and an imperviouswrapping totally inclosing the same.

5. An insulating barrier comprising an oil soaked absorbent sheet, asheet of insulating material at one sidethereof and an imperviouswrapping totally inclosing the same.

In witness whereof, I have hereunto set my hand this 24th day of Aug.1916.

WILLIS ALDEN ISHLER.

